Piezoelectric and flexoelectric properties play an important role in many applications, such as sensors, actuators, and energy generators. A piezoelectric material can have an electrical field induced when a homogeneous strain is applied, and materials exhibiting flexoelectricity can have a spontaneous electrical polarization when induced by a strain gradient. Unlike piezoelectricity which requires structures with no inversion symmetry, flexoelectricity can emerge even in centrosymmetric materials due to the inhomogeneous strain locally breaking inversion symmetry.
Several polymers exhibit piezoelectric and flexoelectric responses, such as polyvinylidene fluoride (PVDF) and polyamides. The polymer crystallites can be oriented by poling using a high electric field at an elevated temperature. Poling can be difficult to control and can result in burning and charring of the polymeric film or coating.